Thermal control of optical filter with local silicon frame

ABSTRACT

Briefly, in accordance with one or more embodiments, a thermally controlled optical filter comprises a frame coupled to an etalon where the frame includes a resistive thermal device disposed on the frame to obtain thermal measurements of the etalon during operation. The frame may be generally L-shaped or generally square-shaped. The frame may include a fillet that is generally planar, generally beveled or trapezoidal, or generally circular in shape. A heater may be additionally disposed on the frame. The etalon and frame subassembly may be bonded to a micro hot plate that is capable of heating the etalon to an operational temperature.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation Application of U.S. patentapplication Ser. No. 13/102,910 filed on May 6, 2011, which is aDivisional of U.S. patent application Ser. No. 12/825,066, filed on Jun.28, 2010 (now U.S. Pat. No. 7,961,374), which is a Divisional of U.S.patent application Ser. No. 11/731,223 (now U.S. Pat. No. 7,771,071),filed on Mar. 30, 2007.

BACKGROUND

Thermally controlled optical filters may inadvertently provide thermalcross talk between the temperature of the filter and other sources oftemperature variation, for example from the case in which the opticalfilter is disposed, from the substrate on which the optical filter ismounted, for from another filter disposed proximate to the filter.Furthermore, varying stresses may be imparted on the filter for examplevia coefficient of thermal expansion (CTE) mismatches and processvariations, which may impact the stability of the filter and thereliability of the frequency at which the filter operates to select adesired wavelength of laser light.

DESCRIPTION OF THE DRAWING FIGURES

Claimed subject matter is particularly pointed out and distinctlyclaimed in the concluding portion of the specification. However, suchsubject matter may be understood by reference to the following detaileddescription when read with the accompanying drawings in which:

FIG. 1 is diagram of thermally controlled optical filters in accordancewith one or more embodiments;

FIG. 2 is a diagram of thermally controlled optical filters including aresistive temperature device formed as a generally L-shaped frame inaccordance with one or more embodiments;

FIG. 3 is a diagram of a thermally controlled optical filter including aresistive temperature device formed as a generally L-shaped frame havinga generally circular fillet in accordance with one or more embodiments;

FIG. 4 is a diagram of resistive temperature devices formed in L-shapedframes bonded to an optical filter wafer in accordance with one or moreembodiments; and

FIG. 5 is a diagram of a thermally controlled optical filter including aresistive temperature device formed in a generally square shaped framein accordance with one or more embodiments.

It will be appreciated that for simplicity and/or clarity ofillustration, elements illustrated in the figures have not necessarilybeen drawn to scale. For example, the dimensions of some of the elementsmay be exaggerated relative to other elements for clarity. Further, ifconsidered appropriate, reference numerals have been repeated among thefigures to indicate corresponding and/or analogous elements.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth to provide a thorough understanding of claimed subject matter.However, it will be understood by those skilled in the art that claimedsubject matter may be practiced without these specific details. In otherinstances, well-known methods, procedures, components and/or circuitshave not been described in detail.

In the following description and/or claims, the terms coupled and/orconnected, along with their derivatives, may be used. In particularembodiments, connected may be used to indicate that two or more elementsare in direct physical and/or electrical contact with each other.Coupled may mean that two or more elements are in direct physical and/orelectrical contact. However, coupled may also mean that two or moreelements may not be in direct contact with each other, but yet may stillcooperate and/or interact with each other. Furthermore, the term“and/or” may mean “and”, it may mean “or”, it may mean “exclusive-or”,it may mean “one”, it may mean “some, but not all”, it may mean“neither”, and/or it may mean “both”, although the scope of claimedsubject matter is not limited in this respect.

Referring now to FIG. 1, a diagram of thermally controlled opticalfilters in accordance with one or more embodiments will be discussed. Asshown in FIG. 1, a thermally controlled optical filter may generallycomprise a hot plate type structure, for example a micromachined siliconfilter 108 having an optical etalon 112 disposed thereon. Filter 110 mayinclude a resistive temperature device (RTD) 118 and heater 116 that maybe utilized to heat etalon 112 to an operational temperature and to taketemperature measurements of the temperature of etalon 112 to select andcontrol the temperature of etalon 112, for example in a feedbackarrangement. Etalon 112 may comprise glass or a similar material and maybe utilized to filter laser light from a laser (not shown) to tune thelaser to a desired operational wavelength. In one or more embodiments,such a laser may comprise, for example, an external cavity laser. Suchtuning of the wavelength of laser light passing through etalon 112 maybe at least partially accomplished via controlling the temperature ofetalon 112, however the scope of the claimed subject matter is notlimited in this respect.

In one or more embodiments, optical filter 110 may comprise etalon 114adhered to glass plate 122 which in turn may be adhered to resistivetemperature device and heater 118. Etalon 114 may be adhered to glassplate 122 and/or glass plate 122 may be adhered to micro hot plate 120having a resistive temperature device 118 and heater 116, for exampleusing an epoxy or similar type of adhesive, although the scope of theclaimed subject matter is not limited in this respect.

Optical filter 110 may provide thermal isolation as well as mechanicalisolation of resistive temperature device 118 and heater 116. Such anarrangement may generally provide minimal cross-talk between thetemperature of filter 110 and any external thermal load, for examplecase temperature and/or substrate temperature. Optical filter 110 mayprovide a simpler arrangement for controlling the temperature of etalon114 resulting in a simpler assembly and manufacturing process. In suchan arrangement, any increased cross talk between the temperature ofoptical filter 110 and the temperature of the case and other filtersand/or the sled temperature may be addressed as described herein.Furthermore, any strain on resistive thermal device 118 and heater 116induced by coefficient of thermal expansion (CTE) type effects and/orprocessing condition, for example due to relaxation of such strain overtime, and any resulting error in temperature measurements, likewise maybe addressed as described herein.

Referring now to FIG. 2, a diagram of optically controlled opticalfilters including a resistive temperature device formed as a generallyL-shaped frame in accordance with one or more embodiments will bediscussed. As shown in FIG. 2, optical filter 210 may be constructed toinclude resistive thermal device 118 comprising a generally L-shapedframe 212. Such an L-shaped frame may provide a more precise measurementof the temperature of etalon 114 and further may provide reduced crosstalk and/or reduced processing stress on resistive thermal device 118due to, for example, coefficient of thermal expansion (CTE) mismatch andprocess type effects. In one or more embodiments, L-shaped frame 212 maycomprise a highly thermally conductive material including but notlimited to silicon (Si), tungsten copper (WCu), silicon carbide (SiC),and so on. L-shaped frame 212 may be disposed on micro hot plate 120with heater 116 wherein an electrical connection between resistivethermal device 118 and micro hot plate 120 with heater 116 may becoupled, for example, using solder or wirebond. Such an L-shaped frame212 for resistive thermal device 118 may be compatible with thin filmprocesses to ad platinum/titanium (Pt/Ti) traces on resistive thermaldevice 118 in addition to one or more gold pads for solder or wirebondtype connections. In one embodiment, L-shaped frame 212 may be arrivedat via a dry etched process such as L-shaped frame 212 of optical filter210, or alternatively L-shaped frame 212 of optical filter 214 may bearrived at, for example, via a wet etched process of silicon. In one ormore embodiments, L-shaped frame 212 may comprise fillet 218 having oneor more surfaces disposed at right or nearly right angles, and in one ormore alternative embodiments, L-shaped frame 212 may comprise fillet 220having one or more beveled or trapezoidal type surfaces, although thescope of the claimed subject matter is not limited in these respects. Inone or more embodiments, etalon 114 may include an area 216 throughwhich laser light may pass there through proximate to fillet 218 orfillet 220, although the scope of the claimed subject matter is notlimited in these respects.

Referring now to FIG. 3, a diagram of a thermally controlled opticalfilter including a resistive temperature device from as a generallyL-shaped frame having a generally circular fillet in accordance with oneor more embodiments will be discussed. As shown in FIG. 3, L-shapedframe 212 may comprise a generally circular fillet 310. In such anembodiment, circular fillet 310 may maximize, or nearly maximize, thecontact area between L-shaped frame 212 and etalon 114 while reducing oreliminating clipping of the laser beam passing through area 216 ofetalon 114, although the scope of the claimed subject matter is notlimited in this respect.

Referring now to FIG. 4, a diagram of resistive temperature devicesformed in L-shaped frames bonded to an optical filter wafer inaccordance with one or more embodiments will be discussed. As shown inFIG. 4, L-shaped frames 212 may be processed using a standard typemicromachined silicon technology or the like. In one or moreembodiments, L-shaped frames 212 of resistive thermal devices 118 may beetched and then bonded to a wafer of etalons 114 prior to dicing andthen subsequently diced to arrive at optical filter subassemblies.Further as shown in FIG. 4, in one embodiment L-shaped frames 212 may beformed via a dry etched wafer 410 or alternatively via a wet etchedwafer 114, although the scope of the claimed subject matter is notlimited in these respects.

Referring now to FIG. 5, a diagram of a thermally controlled opticalfilter including a resistive temperature device formed in a generallysquare shaped frame in accordance with one or more embodiments will bediscussed. As shown in FIG. 5, a thermally controlled optical filter maybe constructed with a square-shaped frame 510 rather than with anL-shaped frame 212. In such an arrangement, square-shaped frame 510 mayinclude a circular opening 512 having resistive thermal device 118disposed along a circumference of circular opening 512. In one or moreembodiments, square-shaped frame 510 may include circular opening 512having resistive thermal device 118 disposed along a circumference ofcircular opening 512 and may further include a heater 514 also disposedalong a circumference of circular opening 512. It should be noted thatL-shaped frame 212 and square-shaped frame 510 are merely example framesthat may include resistive thermal device 118 and/or heater 116, whereinother shapes of frames likewise may be utilized, and the scope of theclaimed subject matter is not limited in these respects.

Although the claimed subject matter has been described with a certaindegree of particularity, it should be recognized that elements thereofmay be altered by persons skilled in the art without departing from thespirit and/or scope of claimed subject matter. It is believed that thesubject matter pertaining to thermal control of optical filter withlocal silicon frame and/or many of its attendant utilities will beunderstood by the forgoing description, and it will be apparent thatvarious changes may be made in the form, construction and/or arrangementof the components thereof without departing from the scope and/or spiritof the claimed subject matter or without sacrificing all of its materialadvantages, the form herein before described being merely an explanatoryembodiment thereof, ad/or further without providing substantial changethereto. It is the intention of the claims to encompass and/or includesuch changes.

1. A method, comprising: forming two or more frames from a first wafer;forming two or more etalons from a second wafer; disposing a resistivethermal device on each of the two or more frames; dicing the first waferand the second wafer; and bonding each of the frames to a correspondingone of the etalons to form optical subassemblies of optical filters. 2.The method of claim 1, wherein the frames have different outsidedimensions than the etalons.
 3. The method of claim 2, wherein theframes have at least one larger outside dimension than the etalons. 4.The method of claim 1, wherein the first wafer comprises a thermallyconductive material and the second wafer comprises a wafer of etalons.5. The method of claim 4, wherein the thermally conductive materialcomprises silicon (Si), tungsten copper (WCu), or silicon carbide (SiC).6. The method of claim 4, wherein said forming comprises a dry etchprocess or a wet etch process, or combinations thereof, to define thetwo or more frames on the first wafer.
 7. The method of claim 1, furthercomprising bonding one of the optical filters onto a micro hot plate. 8.The method of claim 1, further comprising disposing a heater on each ofthe two or more frames.
 9. The method of claim 1, wherein said formingcomprises forming generally L-shaped frames.
 10. The method of claim 9,wherein the generally L-shaped frames each include a fillet having atleast one of right angled surfaces, planar surfaces, beveled surfaces,trapezoidal surfaces, or a circular surface.
 11. The method of claim 1,wherein said forming two or more frames comprises forming generallysquare shaped frames each having a substantially circular opening. 12.The method of claim 11, wherein each of the resistive thermal devices isdisposed along a circumference of the substantially circular opening ofeach of the generally square shaped frames.